Yawn­ing wakes us up

Pretoria News Weekend - - HEALTH -

WHY DO we yawn even after a long night’s sleep?

Yawn­ing is not di­rectly linked to the num­ber of hours of sleep we’ve had, but is an evo­lu­tion­ary re­sponse to changes in our alert­ness.

That’s why we tend to yawn be­fore or after sleep and at times of stress, says Si­mon Thomp­son, pro­fes­sor of clin­i­cal psy­chol­ogy and neu­ropsy­chol­ogy at Bournemouth Univer­sity.

A re­cent the­ory is that it’s linked to the stress hor­mone cor­ti­sol, which raises the tem­per­a­ture of the brain.

“Yawn­ing is thought to al­low more oxy­gen into our lungs be­cause this re­duces our brain’s tem­per­a­ture,” says Thomp­son.

Ac­cord­ing to the the­ory, after a good night’s sleep we yawn be­cause our brain’s tem­per­a­ture is still too high.

“We re­lease cor­ti­sol to wake us up so we yawn un­til it falls to nor­mal lev­els.” – Daily Mail

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